1. Field of the Invention
A total joint replacement (TJR) is a medical procedure that involves the repair and replacement of joints, such as hips and knees. In these surgical procedures, the bones at the hip or knee joints receive orthopedic implants that mimic the structure of the joint that is replaced.
In some cases, infection occurs and this is can be a devastating complication of TJR surgeries. Unless an infection is properly diagnosed within the first two to four weeks following the original surgery (which is uncommon), the infected implant must be removed in combination with an extensive debridement of the surrounding joint tissue and bone.
The current standard of care for treatment of an infected TJR in the United States typically involves a two-stage re-implantation process. In the first stage of this process, the infected components are surgically exposed by incision. Scar tissue is then de-bulked and other soft tissue may be released, and sometimes an osteotomy is performed. This stage also includes the removal of all prosthetic components and foreign material including, for example, acrylic bone cement. After extensive joint debridement of infected soft tissue and bone, a spacer block consisting of heavily dosed antibiotic bone cement is placed temporarily into the joint space. The purpose of the antibiotic bone cement is to sterilize the joint environment and to serve as an antibiotic delivery system. Additionally, the bone cement acts as a spacer to preserve joint space and maintains ligament length. However, the antibiotic released by the bone cement is uncontrolled and is quite costly to use. In addition, more operating room time is necessary to prepare this spacer material. This increases the cost of the operation
Following the removal of the infected implant and the insertion of the antibiotic bone cement spacer, the patient must generally wait between six and twelve weeks before the second stage of the procedure can be performed. This period of time is necessary so that medical professionals can be confident that the infection has been successfully eradicated. Only after the infectious condition has been eliminated, may the second stage proceed. During the second stage, the new prosthesis is re-implanted.
In other countries, such as throughout Europe, a one-stage re-implantation process has been popular. This involves the removal of the infected implant, as noted above, followed by aggressive debridement and then immediate re-implantation of a new implant. The success rate for this technique has typically been lower than the two-stage procedure. The one-state implantation process is generally reserved for patients who are considered to be too feeble or sick to undergo the traditional two-stage re-implantation process.
In certain situations, both one- and two-stage procedures can have disadvantages. For example, and as noted above, the two-stage re-implantation process requires six to twelve weeks between operations. This is a very difficult time for the patient as they do not have a functional joint in place and it is typically very painful to mobilize or ambulate with an antibiotic spacer. Articulating spacers are somewhat better than static spacers, but are also more expensive as well as more difficult and time-consuming to place during the original stage one procedure. From a health care standpoint, the two-stage procedure also requires two separate hospitalizations. Finally, from a surgeon's standpoint, a significant amount of scar tissue develops during the time span between the two procedures. This makes for a very difficult and time-consuming second stage operation. In addition, the two-stage re-implantation process involves not one, but two, very difficult and costly surgical procedures.
On the other hand, a one-stage re-implantation surgical protocol requires absolute identification of the infecting organism in order to proceed. Unfortunately, it is very difficult to achieve this absolute identification in the current health care system. In addition, a one-stage re-implantation protocol requires the use of fully-cemented components. Fully-cemented components are typically not favored by U.S. surgeons for revision surgery because they require a high amount of antibiotic which may structurally weaken the cement.
Moreover, and in both one-stage and two-stage re-implantation surgical protocols, the release of the antibiotic from the bone cement is completely uncontrolled. This is a significant disadvantage of both protocols and essentially acts to lengthen the time between the first and the second surgical procedures in the two-stage re-implantation process.
Thus, there remains a need for a device that may be employed during re-implantation surgical procedures that may be used to deliver antibiotic or other therapeutic agents in a controlled and titratable manner directly into the synovial joint cavity and adjoining medullary canals as a means of eliminating the infection following the removal of a previous orthopedic implant. In addition, there remains a need for such a device that can provide stability and maintain the physical dimensions of joint space and normal soft tissue envelope in any joint undergoing the re-implantation of an orthopedic implant. In addition, there remains a need for such a device that may be easily employed, facilitates the reduction in the time needed to conduct the stage one re-implantation surgery and that reduces the overall time between the first and second stages of a two-stage re-implantation surgical protocol. At least some of these will be addressed by the devices and methods described herein.
2. Description of the Background Art
Other patents which disclose devices and methods for delivery of an antiobiotic to an intramedullary canal include: U.S. Pat. Nos. 8,900,323; 8,900,322; and 8,454,706.